Eberspacher Airtronic D2 heater.

I have had experience of both Eberspacher and Webasto heaters on yachts and to be honest both were a constant source of irritation because of faults.  Mainly, though, due to the use of red diesel rather than electrical problems.  If yours is the same type of system, there should be a way of pressing certain buttons on the control pad to generate fault codes which show up as flashing lights in a sort of morse code pattern - there should be details on the internet.  That should pinpoint exactly where the fault lies.